1. Click on the following link https://resident.uidai.net.in/find-uid-eid or simple type " search Aadhar card by mobile number" on www.google.com
2. After clicking on the above link, you will find out a one form that will look like below picture-
4. Finally type OTP number on the box "Enter OTP" shown in the form and then click on "Verify OTP".
After doing all steps, you will get your Aadhaar card number on your registered mobile number as a message. Also you can download your Aadhaar card.
If you have any query then please comment me. i will try to solve your query.
Have a nice day.